Finish Riley's monster commit

3b38d725d7
May the Gods have mercy on my soul.

Shared/Errors/ALTLocalizedError.swift

@@ -0,0 +1,182 @@
+//
+//  ALTLocalizedError.swift
+//  AltStore
+//
+//  Created by Riley Testut on 10/14/22.
+//  Copyright © 2022 Riley Testut. All rights reserved.
+//
+
+import Foundation
+import AltSign
+
+public let ALTLocalizedTitleErrorKey = "ALTLocalizedTitle"
+public let ALTLocalizedDescriptionKey = "ALTLocalizedDescription"
+
+public protocol ALTLocalizedError<Code>: LocalizedError, CustomNSError, CustomStringConvertible
+{
+    associatedtype Code: ALTErrorCode
+
+    var code: Code { get }
+    var errorFailureReason: String { get }
+
+    var errorTitle: String? { get set }
+    var errorFailure: String? { get set }
+
+    var sourceFile: String? { get set }
+    var sourceLine: UInt? { get set }
+}
+
+public extension ALTLocalizedError
+{
+    var sourceFile: String? {
+        get { nil }
+        set {}
+    }
+
+    var sourceLine: UInt? {
+        get { nil }
+        set {}
+    }
+}
+
+public protocol ALTErrorCode: RawRepresentable where RawValue == Int
+{
+    associatedtype Error: ALTLocalizedError where Error.Code == Self
+
+    static var errorDomain: String { get } // Optional
+}
+
+public protocol ALTErrorEnum: ALTErrorCode
+{
+    associatedtype Error = DefaultLocalizedError<Self>
+
+    var errorFailureReason: String { get }
+}
+
+/// LocalizedError & CustomNSError & CustomStringConvertible
+public extension ALTLocalizedError
+{
+    var errorCode: Int { self.code.rawValue }
+
+    var errorDescription: String? {
+        guard (self as NSError).localizedFailure == nil else {
+            // Error has localizedFailure, so return nil to construct localizedDescription from it + localizedFailureReason.
+            return nil
+        }
+
+        // Otherwise, return failureReason for localizedDescription to avoid system prepending "Operation Failed" message.
+        return self.failureReason
+    }
+
+    var failureReason: String? {
+        return self.errorFailureReason
+    }
+
+    var errorUserInfo: [String : Any] {
+        let userInfo: [String: Any?] = [
+            NSLocalizedFailureErrorKey: self.errorFailure,
+            ALTLocalizedTitleErrorKey: self.errorTitle,
+//            ALTSourceFileErrorKey: self.sourceFile, // TODO: Figure out where these come from
+//            ALTSourceLineErrorKey: self.sourceLine,
+        ]
+
+        return userInfo.compactMapValues { $0 }
+    }
+
+    var description: String {
+        let description = "\(self.localizedErrorCode) “\(self.localizedDescription)”"
+        return description
+    }
+}
+
+/// Default Implementations
+public extension ALTLocalizedError where Code: ALTErrorEnum
+{
+    static var errorDomain: String {
+        return Code.errorDomain
+    }
+
+    // ALTErrorEnum Codes provide their failure reason directly.
+    var errorFailureReason: String {
+        return self.code.errorFailureReason
+    }
+}
+
+/// Default Implementations
+public extension ALTErrorCode
+{
+    static var errorDomain: String {
+        let typeName = String(reflecting: Self.self) // "\(Self.self)" doesn't include module name, but String(reflecting:) does.
+        let errorDomain = typeName.replacingOccurrences(of: "ErrorCode", with: "Error")
+        return errorDomain
+    }
+}
+
+public extension ALTLocalizedError
+{
+    // Allows us to initialize errors with localizedTitle + localizedFailure
+    // while still using the error's custom initializer at callsite.
+    init(_ error: Self, localizedTitle: String? = nil, localizedFailure: String? = nil)
+    {
+        self = error
+
+        if let localizedTitle
+        {
+            self.errorTitle = localizedTitle
+        }
+
+        if let localizedFailure
+        {
+            self.errorFailure = localizedFailure
+        }
+    }
+}
+
+public struct DefaultLocalizedError<Code: ALTErrorEnum>: ALTLocalizedError
+{
+    public let code: Code
+
+    public var errorTitle: String?
+    public var errorFailure: String?
+    public var sourceFile: String?
+    public var sourceLine: UInt?
+
+    public init(_ code: Code, localizedTitle: String? = nil, localizedFailure: String? = nil, sourceFile: String? = #fileID, sourceLine: UInt? = #line)
+    {
+        self.code = code
+        self.errorTitle = localizedTitle
+        self.errorFailure = localizedFailure
+        self.sourceFile = sourceFile
+        self.sourceLine = sourceLine
+    }
+}
+
+/// Custom Operators
+/// These allow us to pattern match ALTErrorCodes against arbitrary errors via ~ prefix.
+prefix operator ~
+public prefix func ~<Code: ALTErrorCode>(expression: Code) -> NSError
+{
+    let nsError = NSError(domain: Code.errorDomain, code: expression.rawValue)
+    return nsError
+}
+
+public func ~=(pattern: any Swift.Error, value: any Swift.Error) -> Bool
+{
+    let isMatch = pattern._domain == value._domain && pattern._code == value._code
+    return isMatch
+}
+
+// These operators *should* allow us to match ALTErrorCodes against arbitrary errors,
+// but they don't work as of iOS 16.1 and Swift 5.7.
+//
+//public func ~=<Error: ALTLocalizedError>(pattern: Error, value: Swift.Error) -> Bool
+//{
+//    let isMatch = pattern._domain == value._domain && pattern._code == value._code
+//    return isMatch
+//}
+//
+//public func ~=<Code: ALTErrorCode>(pattern: Code, value: Swift.Error) -> Bool
+//{
+//    let isMatch = Code.errorDomain == value._domain && pattern.rawValue == value._code
+//    return isMatch
+//}